#! /usr/bin/python

# Largest prime factor
#
# The prime factors of 13195 are 5, 7, 13 and 29.
# What is the largest prime factor of the number 600851475143 ?

n = 600851475143
i = 2
while i * i < n: 
    while n % i is 0:
        n = n / i
    i += 1
print n
